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A Presentation On GSM Based Wireless Electronic Notice Board using LED. Submitted By: P.A. Murthy M. Anusha Hanuma Kumari. Submitted To:
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The design of the project is basically divided into:
1. Transmitting Section
2. Receiving Section
Transmitting Section consists of just mobile which has inbuilt GSM modem for wireless data transfer through GSM.
GSM (Global System for Mobile communications: originally from Group Special Mobile) is the most popular standard for mobile phones in the world.
Since it is a multiuser system, various users are authenticated to use the system or display messages on the notice board.
For security, password is provided to authorized users. Before sending message, a user need to authenticate itself with the system by sending the assigned password to the receiver section’s SIM number.
The receiving section’s system verifies password and sends response to the user and tells it to send the message.
To prevent misuse, user is provided with a die-out time before which it has to send message , after which authentication expires. User has to authenticate again if it does not sends message within that die-out time.
GSM is a cellular network, which means that mobile phones connect to it by searching for cells in the immediate vicinity.
The modulation used in GSM is Gaussian minimum-shift keying (GMSK), signal to be modulated onto the carrier is first smoothed with a Gaussian low pass filter prior to being fed to a frequency modulator which greatly reduces adjacent channel interference).
Microcontroller is the heart of the system. It is used for interfacing the display, memory and other peripherals with GSM modem.
The microcontroller used in this case is AT89c52. It is a low-power, high performance CMOS 8-bit microcomputer with 8K bytes of Flash programmable and erasable read only memory.
It is compatible with the industry-standard 80C51 and 80C52 instruction set and pin out.
A GSM modem is a wireless modem that works with a GSM wireless network. It sends and receives data through radio waves. Here we are GSM Modem of mobile.
Modem interfaces to the host via Universal serial receiver-transmitter (USART), which is automatically detected by the operating system and easily configured using standard operating system drivers. The modems are controlled by industry standard AT commands.
AT commands are used to control modems by microcontroller.
The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to supply EIA-232 voltage levels from a single 5-V supply and converts EIA- 232 inputs to 5-V TTL/CMOS levels.
The microcontroller is interfaced with PC via MAX232level convertor.It is used to convert RS232 voltage to TTL voltage levels and vice versa. We use PC's serial port to interface microcontroller.
In PC, at RS-232 voltage levels, logic 1 varies from -3 to -15 volts and logic 0 from +3 to +15 volts. The microcontroller which works on TTL logic levels, logic 1 is +5 volts and logic 0 is 0 volts. Therefore to interface the two we use a MAX 232 driver IC.
One of the most common devices attached to an 8051 is an LCD display. Here we have used 16x2 Hitachi HD44780 compatible module, having 16 pins including 2 pins for backlight.
Power Supply is an important part of a circuit. It provides required supply to different blocks of the circuit from input 230 VAC.
Express PCB is free PCB software and is a snap to learn and use. With this, designing circuit boards is simple for the beginner and efficient for the professional.
B. Embedded C:
Embedded C is language for programming microcontroller for embedded applications. There is a large - and growing – international demand for programmers with 'embedded' skills, and many desktop developers are starting to move into this important area
Keil is basically compiler to compile embedded C programs. The Keil 8051 Development Tools are designed to solve the complex problems facing embedded software developers.
Visual Basic (VB) is an event driven programming language and associated development environment from Microsoft for its COM programming model. Visual Basic was derived from BASIC and enables the rapid application development (RAD) of graphical user interface (GUI) applications.
Microcontroller coding will be done using Embedded C and Kiel.
PC Coding will be done using Visual Basic(VB). Nokia PC Connectivity SDK is a tool used in VB for GSM Modem interfacing.
We can use a PC with administrator for ease of message sending and keeping records.
Alphanumeric LCDs have a limitation on size as well as no of characters. These can be replaced with large LED display boards
Robots can be controlled in a similar fashion by sending the commands to the robots.